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NOTE: Employers in states with state-run safety and health plans should check with their state agency. Their state may enforce standards that, while "as effective as federal standards," may not be identical to the federal requirements.

What is a confined space?

A confined space has limited or restricted means of entry or exit, is large enough for an employee to enter and perform assigned work, and is not designed for continuous occupancy by the employee.

Examples of confined spaces are:

Underground vaults,

Tanks,

Storage bins,

Pits and diked areas,

Vessels, and

Silos.

What are the hazards that may be associated with confined spaces?

Because of the difficulties of entry and exit from confined spaces, employees who work in them may also face increased risk of exposure to serious injury from hazards such as entrapment, engulfment, and hazardous atmospheric conditions.

The atmosphere in a confined space can be hazardous due to the presence of chemicals that are either man-made, such as toxic fumes from welding operations, or naturally occurring, such as hydrogen sulfide or methane that can result from decomposing organic material. The oxygen level in a confined space may be reduced below that required for normal breathing. Gases that are heavier than air, such as carbon dioxide, may sink to the bottom of a confined space and reduce the level of oxygen breathed by a worker. Or chemical processes such as the formation of rust or bacterial action, as in the fermentation process, can use up the oxygen in a confined space.

In addition, the presence of flammable liquids or gases in a confined space presents a fire or explosion hazard

Work in confined spaces may keep employees closer to machinery components and power-driven equipment, such as augers, than they would be otherwise.

Heat, noise, vibration, and structural hazards such as scaffolding installed for maintenance, overhead structural members, or baffles also contribute to potentially unsafe conditions in confined spaces.

How does OSHA regulate confined spaces?

OSHA regulates confined spaces that have one or more of the following characteristics:

contains or has the potential to contain a hazardous atmosphere;

contains a material that has the potential for engulfing an entrant;

has an internal configuration that might cause an entrant to be trapped or asphyxiated by inwardly converging walls or by a floor that slopes downward and tapers to a smaller cross section; and/or

The tank was located on the second floor and was part of a chicken processing operation at a rendering plant. The inside of the tank measured 8 feet high by 6-1/2 feet in diameter. The bottom of the tank was cone-shaped and sloped outward at a 120-degree angle. The to of the tank was covered with loose plate steel, one-third of which had been removed just prior to employee’s entry. Employee was to enter the tank to repair a hole in the bottom. The only witnesses to this operation were two other employees who observed from outside the tank. Upon entering the tank, the employee was immediately overcome by a gaseous, oxygen-deficient atmosphere. When he tried to climb out, he fell backward into the tank and apparently lost consciousness. Local authorities were unable to revive him. The gas present in the tank was identified as methane.

Provide, maintain, and require, at no cost to the employee, the use of personal protective equipment and any other equipment necessary for safe entry (e.g., testing, monitoring, ventilating, communicating, and lighting equipment; barriers, shields, and ladders);

Ensure that at least one attendant is stationed outside the permit space for the duration of entry operations;

Coordinate entry operations when employees of more than one employer are to be working in the permit space;

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